The emergence of Sarah Palin as a political force in the presidential race has left many top Democrats fretting that, just two weeks after their convention ended on an emotional high, Barack Obama’s campaign has suddenly lost its stride.

Obama has responded aggressively this week to Palin’s presence on the Republican ticket, using TV ads and campaign rallies to attack her contention that she is a political reformer who will take on the Washington establishment — a role Obama has long claimed as his alone.

But some Democrats are now worried about the perils of Obama’s strategy, saying that his campaign, instead of engaging the Alaska governor, should avoid any move that draws more attention to her and could enhance her appeal among the white, blue-collar voters who remain cool to Obama’s candidacy.

A series of new polls suggests that Palin has given a major boost to John McCain’s campaign, exciting the GOP base, winning over white women and all but erasing Obama’s lead.

Concern among Democrats was high enough Tuesday that Sen. Richard J. Durbin (D-Ill.), one of Obama’s strongest supporters, felt it necessary to cite historical polling data at a lunch of Democratic senators to convince them that post-convention “bounces,” such as the one that has followed last week’s GOP convention, have often faded in past elections.

To reassure nervous lawmakers, Durbin also reviewed Democratic registration gains this year in key battleground states.

Still, Democrats expressed anxiety about the new challenge suggested by recent surveys showing McCain has gained ground among independent voters and women, who could decide the race in states such as Ohio, Michigan, Pennsylvania and Virginia.

A new Wall Street Journal/NBC News poll released Tuesday, for instance, shows that McCain is now winning among white women 52% to 41% after having been statistically tied with Obama in that crucial category just a month ago.

“Whenever you see that kind of movement, you ought to be concerned; you ought to try to address it,” said Rep. Elijah E. Cummings (D-Md.), a strong Obama backer.

David Bonior, the former Michigan congressman who managed Democrat John Edwards’ unsuccessful presidential bid, called the new poll findings a “real concern,” adding: “We can’t lose white women and expect to do well in this race.”

Im sorry for the watermark on video. I couldnt afford the full version of the video editor. The video file I downloaded is too big for me to edit so I had to use this method. This and a few other comments Biden made in this speech were too priceless to pass up